eucalyptus
( yoo - kuh - LIP - tuss )
At-A-Glance Information
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Commonly known as Eucalypts or Gum Trees, plants in this genus of evergreen shrubs and trees need full sun and little to no water to perform well. Their fragrant foliage is commonly used in cut flower arrangements as filler greenery, and the plants themselves range from sprawling shrubs to giant trees. They are the most commonly planted non-native tree in both California and Arizona, where they are used as windbreaks, shade trees, firewood and timber. They have attractive bark, inconspicuous flowers, and woody seed capsules. Take care when planting these trees in the landscape, as plant parts are toxic to humans and animals if ingested.
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eucalyptus Species and Varietals
The genus Eucalyptus is a member of the plant family Myrtaceae and includes over 700 distinct species. The best growing zones for Eucalyptus are 6, 6, 8-24 H1 and H2. To find your zone, click here: Zone Map.
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Eucalyptus cinerea (Silver Dollar Tree) This species is hardy to around 15 degrees Fahrenheit and reaches 20-50 feet tall and 20-40 feet wide. New leaves are grey-green and heart-shaped and older leaves are narrow and green. Withstands wind and can be used in dry sites or sloped areas. |
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Eucalyptus citriodora (Corymbia citriodora) (Lemon-Scented Gum) This species is hardy down to around 26 degrees Fahrenheit, and reaches 45-90 feet tall and 15-45 feet wide. Mature leaves are gold-green lemon-scented and bark is smooth and powdery white. This tree is narrow, and can be grown against walls and fences. Stake young trees; their trunks are weak. Cut back and thin often to strengthen the trunk. |
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Eucalyptus cladocalyx (Sugar Gum) Hardy to 25 degrees Fahrenheit, this species reaches 45-90 feet tall and 45-75 feet wide, It has a stout trunk and clusters of puffy foliage separated by open spaces. Leaves are shiny red and bark is pale grey, peeling, and reveals white patches. Flowers are creamy yellow and bloom profusely in summertime. Variety 'Nana' is a dwarf variety reaching 20-25 feet tall and serves as a great windbreak. |
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Eucalyptus conferruminata (Bushy Yate) Hardy down to around 26 degrees Fahreheit, this species of Eucalyptus is usually sold as Eucalyptus lehmannii. It reaches 12-27 feet tall and 15-30 feet wide, with ovular light green leaves that sporadically turn red in fall. Flowers are green and are followed by brown capsules that remain on the branches for a while before dropping. Good for windbreaks or seaside areas. Left unpruned, the lower branches will graze the ground. |
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Eucalyptus dalrympleana (Mountain Gum) This species of Eucalyptus is hardy down to about 10 degrees Fahrenheit, and quickly reaches between 70-120 feet tall and 25-50 feet wide. Leaves are bright green, and bark is smooth and white. This is a great large Eucalyptus species for cooler climates, and can tolerate alkaline soils. |
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Eucalyptus erythrocorys (Red-Cap Gum) This species of Eucalyptus reaches 12-30 feet tall and 9-25 feet wide. Leaves are thick, shiny, and deep green, and bark is white. Flowers are yellow and appear in pom-pom clusters, emerging from underneath red 'caps'. The heaviest bloom occurs in early springtime, but can pop at any time of the year. Naturally and best grown as a multi-trunked tree, it is a sprawling plant but attractive both in and out of bloom. Can be used as a lawn tree, and can take regular garden water. Also a good choice for desert gardens. Hardy to about 24 degrees Fahrenheit. |
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Eucalyptus ficifolia (Corymbia ficifolia) (Red-Flowering Gum) This species is hardy down to about 28 degrees Fahrenheit, and reaches 18-45 feet tall and 15-60 feet wide. It usually takes the form of a single-trunked round-headed tree, with deep green leaves and foot-long clusters of red (sometimes pink, white, cream, or orange) flowers that peak in summertime. Seed capsules are heavy; prune from younger trees to avoid the weight bringing down the branches. |
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Eucalyptus gunnii (Cider Gum) This species is hardy down to about 8 degrees Fahrenheit, and reaches 30-75 feet tall and 18-45 feeet wide. Foliage is silvery blue-green when young, and matures to dark green. Bark is green and tan. This is one of the quickest growing Eucalyptus species, and is hardy to boot! It has a dense habit, making it a great choice for windbreaks, screens, or as a shade tree. The foliage from this tree is commonly used in cut flower arrangements as filler greenery. |
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Eucalyptus leucoxylon (White Iron-Bark) This species is hardy to 16 degrees Fahrenheit, and reaches 30-90 feet tall and 18-60 feet wide. It is a slender upright and open tree with pendulous branches. Leaves are grey-green, and the trunk is brown to blue-grey, shedding to reveal new white bark. Flower color can be cream, pink, or reddish, and blooms are followed by goblet-shaped capsules. This species can tolerate many harsh conditions, including heat, aridity, wind, heavy soils, and rocky soils. |
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Eucalyptus microtheca (Coolibah) This species forms a bushy, round-headed single or multi-trunked tree that reaches 30-60 feet tall and 24-54 feet wide. Leaves are blue-green and ribbon-like. This is one of the best Eucalyptus species for Arizona's climate, and can tolerate wind. Overall, a neat tree. |
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Eucalyptus 'Moon Lagoon' This species is hardy to around 23 degrees Fahrenheit, and is a hybrid of unconfirmed parentage. It reaches 4-10 feet tall and about as wide, with delicate branches and blue-grey foliage. Flowers are white and open from red buds in spring to summertime. Hard prune each year in early springtime to ensure a fresh batch of new foliage, which is wonderful for arrangements. |
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Eucalyptus neglecta (Omeo Gum) This species is hardy to 0 degrees Fahrenheit, and is one of the hardiest Eucalypts. It reaches 40-60 feet tall and as wide, with round juvenile leaves and foliage that takes on pinkish hues in cooler weather. This is a fast-growing specimen tree and tolerates wet soil conditions relatively well. |
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Eucalyptus nicholii (Nichol's Willow-Leafed Peppermint) This species reaches 36-48 feet tall and 15-36 feet wide, with light green leaves and reddish-brown bark. It is hardy down to about 13 degrees Fahrenheit, and has a graceful, weeping habit. Leaves smell of peppermint when crushed. Can't take a lot of water. |
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Eucalyptus papuana (Blakella papuana) (Ghost Gum) This upright, picturesque tree reaches 30-50 feet tall and 20-35 feet wide. Leaves are light green, tinted purple in frost conditions, and bark is smooth and white. A pretty clean tree, it produces very little litter in comparison to its genus-mates, and is also tough and wind-tolerant. Hardy down to about 21 degrees Fahrenheit. |
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Eucalyptus parvula (Eucalyptus parvifolia) (Small-Leaved Gum) This species is hardy to 0 degrees Fahrenheit, and reaches 25-40 feet tall and 15-30 feet wide, with semi-sweeping branches and light to dark blue-green foliage. Leaves are highly fragrant and bark is tan to grey. Can tolerate poorly draining soil and shade better than other species. Habit is upright and spreading. |
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Eucalyptus polyanthemos (Silver Dollar Gum) This species is hardy to 16 degrees Fahrenheit, and has grey-green nearly round leaves when they are new, dark green and lance-shaped leaves when they are mature. Younger leaves are great in arrangements. These trees are great as street or specimen trees. |
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Eucalyptus pulverulenta (Silver Mountain Gum) Reaches 18-30 feet tall and 6-15 feet wide, with silver-grey juvenile foliage. Bark peels off in ribbons. Flowers are small, fuzzy and creamy white and bloom from fall through springtime. The branches are used commonly in cut flower arrangements. Cut back often to encourage more foliage production. Variety 'Baby Blue' is a wonderful selection of this species. Hardy to 17 degrees Fahrenheit. |
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Eucalyptus salmonophloia (Salmon Gum) This species is hardy to 23 degrees Fahrenheit, and slowly grows to reach 40 feet tall and just as wide. Leaves are narrow and bright green, catching sun well and creating a shimmering effect. Bark is salmon-colored. Can tolerate drought and some salt in the soil. Great for desert landscapes. |
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Eucalyptus salubris (Gimlet) These trees are hardy down to a temperature of 23 degrees Fahrenheit, and reach 20-25 feet tall and just as wide. Foliage is glossy and deep green, and bark is smooth, shiny, and red-brown. Flowers are showy for the genus and creamy white. Can be grown as a single- or multi-trunked tree, and can withstand heavy soils. Good for desert landscapes. |
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Eucalyptus sargentii (Salt River Mallet) This species of Eucalyptus can be grown as either a single- or multi-trunked tree with dark gray, peeling bark. Flowers are cream-colored, opening from slender buds. This is a tough, stout tree that can tolerate a lot of salt. Leaves are narrow and green, and this species is hardy to 22 degrees Fahrenheit. |
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Eucalyptus sideroxylon (Red Iron-Bark) Hardy to 23 degrees Fahrenheit, reaching 30-90 feet tall and 30-60 feet wide. Foliage is blue-green, turning bronze in cooler wintertime temperatures. Trunk is furrowed and nearly black, and flowers are a light pink to crimson, blooming mainly from fall through late spring. Can be either open or dense, slender or squat, or weeping or upright, depending on growing conditions and pruning. Great as a specimen, screen or street tree, and does not do well in wet or heavy soils. |
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Eucalyptus torquata (Coral Gum) Hardy to 20 degrees Fahrenheit, this species reaches 18-36 feet tall and 15-30 feet wide. Foliage is light-green to yellow-green and flowers are coral red to yellow, emerging from lantern-like buds. Blooms sporadically throughout the year. This tree makes great cut flowers and foliage. Great accent tree. |
Caring for and pruning eucalyptus Trees
Something to consider before you plant Eucalyptus trees on your property is that they contain a highly combustible oil, and are therefore very flammable, as is their litter. Do not plant these trees near homes or other structures.
The first step in caring for a Eucalyptus tree or shrub is to choose the right spot for installation. These can be very large trees, so choose a planting site with ample space to accommodate their mature size. Make sure trees will not interfere with buildings, power lines, or other plants as they increase in size. It is also important to note one more time that under no circumstances should these trees be planted near buildings or other structures, as they contain very flammable oils, and therefore present a fire hazard. These trees love full sun, and will need a place in the landscape that receives at least between 6 and 8 hours of direct sun daily. This exposure will encourage healthy growth and enhance their aromatic foliage. These trees prefer well-draining soil, and are tolerant of a wide variety of soil types, but perform best in slightly acidic to neutral soil (with a pH of between 5.5 and 6.5). Poor-draining, heavy clay soils should be amended with plenty of sand and organic matter before tree installation to increase drainage ability. Soil should allow water to flow through easily to avoid root rot issues. Water new trees regularly (especially during hot or dry periods) and deeply, allowing adequate moisture to reach the root zone. A good rule of thumb is to water young Eucalyptus trees when the top few inches of soil is dry to the touch. Established trees are considered very drought-tolerant, though they will still need supplemental deep waterings during extended dry spells to stay healthy. Ensure that soil dries out completely between waterings to avoid issues with root rot.
After installing a Eucalyptus tree, apply a layer of organic mulch around its base to help regulate soil temperature, retain moisture, and suppress weeds. Eucalyptus trees are not heavy feeders, and do not need fertilizing. A yearly application of compost around the base of trees is sufficient for providing nutrients for the growing season. If trees are in particularly poor soil or have pale, yellowing leaves, they may benefit from a feeding with a balanced, slow-release fertilizer in the springtime. Avoid excessive nitrogen fertilization, as it can lead to overly lush growth that is more susceptible to diseases and pests. The ideal time to prune Eucalyptus trees is in late winter to early spring. At this time, dead, crossing, damaged, or diseased branches can be taken off the tree and suckers can be removed from the bases of trees. Take care not to over-prune, as this can stress out the tree and open it up to issues with pests and disease.
The first step in caring for a Eucalyptus tree or shrub is to choose the right spot for installation. These can be very large trees, so choose a planting site with ample space to accommodate their mature size. Make sure trees will not interfere with buildings, power lines, or other plants as they increase in size. It is also important to note one more time that under no circumstances should these trees be planted near buildings or other structures, as they contain very flammable oils, and therefore present a fire hazard. These trees love full sun, and will need a place in the landscape that receives at least between 6 and 8 hours of direct sun daily. This exposure will encourage healthy growth and enhance their aromatic foliage. These trees prefer well-draining soil, and are tolerant of a wide variety of soil types, but perform best in slightly acidic to neutral soil (with a pH of between 5.5 and 6.5). Poor-draining, heavy clay soils should be amended with plenty of sand and organic matter before tree installation to increase drainage ability. Soil should allow water to flow through easily to avoid root rot issues. Water new trees regularly (especially during hot or dry periods) and deeply, allowing adequate moisture to reach the root zone. A good rule of thumb is to water young Eucalyptus trees when the top few inches of soil is dry to the touch. Established trees are considered very drought-tolerant, though they will still need supplemental deep waterings during extended dry spells to stay healthy. Ensure that soil dries out completely between waterings to avoid issues with root rot.
After installing a Eucalyptus tree, apply a layer of organic mulch around its base to help regulate soil temperature, retain moisture, and suppress weeds. Eucalyptus trees are not heavy feeders, and do not need fertilizing. A yearly application of compost around the base of trees is sufficient for providing nutrients for the growing season. If trees are in particularly poor soil or have pale, yellowing leaves, they may benefit from a feeding with a balanced, slow-release fertilizer in the springtime. Avoid excessive nitrogen fertilization, as it can lead to overly lush growth that is more susceptible to diseases and pests. The ideal time to prune Eucalyptus trees is in late winter to early spring. At this time, dead, crossing, damaged, or diseased branches can be taken off the tree and suckers can be removed from the bases of trees. Take care not to over-prune, as this can stress out the tree and open it up to issues with pests and disease.
Propagation
Eucalyptus trees can be propagated in a number of ways, including by seed, cutting, grafting, or micropropagation. The most popular methods are by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method, especially if you are dealing with a hybrid variety. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Eucalyptus, follow the instructions below:
Propagating Eucalyptus by Cutting
Propagating Eucalyptus by Seed
Propagating Eucalyptus by Cutting
- Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
- In late summertime, choose the plant that you'd like to propagate. Ideal cuttings are taken from a tree that is between 2 and 12 months old. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 5 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
- Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
- Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.
Propagating Eucalyptus by Seed
- Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
- Harvest your seeds. The seed pods on Eucalyptus plants are pretty easy to spot, they're large and dangle from the branches, left behind after flowers have faded. Collect ripe seeds when the seed capsules split easily, and place the pods in a bag to contain any seeds that fall out. Once they have all been collected, bring them indoors to work with them. The seeds are very small, so a hard, clean surface is best. Place the seeds in a bowl of warm water, and leave them to soak for 24 hours to soften their seed coat. Any seeds that float can be discarded.
- Caesalpinia seeds have a hard coating that protects them, but this coating also makes it a little difficult to get them to germinate. We can help the process along by scarifying them with sandpaper (or simply rubbing them against an abrasive surface). Do this with as many seeds as you can; they will probably not all sow, and the ones that do will be of varying characteristics. The more seeds you plant, the more chances you will have to get the resulting shrub you want. Place your seeds in lukewarm water for six hours. Viable seeds will sink to the bottom, and non-viable seeds will float to the top. You can discard any seeds that float.
- Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about an eighth of an inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes between 14 and 21 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
- Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Eucalyptus seeds are contained inside of hard seed pods, which remain on branch tips after flowers have faded.
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Eucalyptus seeds are relatively small, and each seed pod can contain hundreds of them.
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Problems and Pests
Eucalyptus trees can suffer from issues with the following pests and diseases:
- Anthracnose
- Armillaria Root Rot
- Canker Diseases
- Collar, Root, and Crown Rot
- Leaf Spot
- Tar Spot
- Powdery Mildew
- Wood Decay or Heart Rot
Gallery
The woody seed capsules produced by Eucalyptus trees are commonly called gumnuts.
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All species of Eucalyptus trees add a layer of bark each year, and the outermost layer dies and is shed.
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Each species has unique leaves, which are commonly used in fresh and dried flower arranging.
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Smaller varieties of Eucalyptus trees are great for home gardens.
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Eucalyptus can make great street trees.
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Eucalyptus can make great shade trees when mature.
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These trees do well in desert and xeriscape landscapes due to their drought and heat tolerances.
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The bright blue-green foliage of many species stands out in the landscape.
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In addition to producing beautiful flowers and foliage, these are also very fragrant plants.
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Videos
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Learn all about these fascinating trees.
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How to grow Eucalyptus from seed.
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Planting and caring for Eucalyptus trees.
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How to care for indoor Eucalyptus plants.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Pages 311 - 313, Eucalyptus
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